IT COULD take five years or longer to clear the scourge of ghost estates after more than 800 were filled in the last year, experts have warned.

There are 2,066 unfinished developments scattered in towns and cities up and down the country with Sligo, Cavan, Leitrim, Roscommon and Longford counties the worst affected.

Minister for Housing and Planning Willie Penrose said a fifth of houses lying vacant in 2010 are now in some sort of use.

"There is no magic wand that can solve this in one fell swoop. It will take time, hard work, co-operation, a willing spirit and not a little patience to see its resolution," he said.

The latest survey of the problem for the Department of the Environment revealed 7,343 dwellings which had been recorded as vacant in 2010 are now occupied.

The analysis showed 18,638 dwellings were recorded as finished but empty - a fall of a fifth in the 23,250 recorded last year - while there are another 17,872 dwellings at various stages of construction, totalling 36,510.

When the hangover from the property bubble was first assessed by independent researchers at NUI Maynooth last year, it showed more than 300,000 empty homes around the country and 600 ghost estates - developments which are abandoned, unoccupied or uncompleted.

Three estates have been demolished.

Professor Rob Kitchin, director of NUI's National Institute of Regional and Spatial Analysis (Nirsa) who first uncovered the massive crisis, said there was good news and bad news.

"Although the level of estates is good, or improving, the level of occupancy is not. It will be another five years before all the empty houses will be filled if they carry on at the same rate," he said.

"If you carried on at that rate for the next year and the year after, it would take another five years to work it all out."

The official survey inspected 2,876 housing developments of two or more units. Since last year it found 701 developments have been completed and 109 developments have not substantially commenced.

Prof Kitchin warned about the lack of progress in the five counties worst affected. He said the problem of no credit for developers and no demand or credit for mortgages in the areas worst affected were huge factors in preventing completion.

"It's going to take a while for these estates to work themselves out. The problem is going to be around for a while," the professor said.

The minister also launched a code of practice to be applied by developers, financial institutions including bad-bank Nama which controls 20 large developments, local authorities and residents.

The Nama sites are among 211 estates given a category four warning tag of being the most problematic from a public safety perspective.